Synonyms: dictatorial, authoritarian, dogmatic, doctrinaire, imperious, overbearing

These adjectives mean asserting or tending to assert one's authority or to impose one's will on others. 

• Dictatorial stresses the highhanded, peremptory manner characteristic of a dictator: ordered the staff about in her usual dictatorial manner. 
• Authoritarian implies the expectation of unquestioning obedience: the timid child of authoritarian parents. 
• Dogmatic suggests the imposing of one's will or opinion as though these were beyond challenge: "When people are least sure, they are often most dogmatic" John Kenneth Galbraith. 
• Doctrinaire implies the imposition of one's theories, beliefs, or doctrines: "They didn't know the facts . . . and I don't think it would've mattered in the slightest if they had. Very doctrinaire" George V. Higgins. 
• Imperious suggests the arrogant manner of one accustomed to commanding: dismissed my opinion with an imperious gesture. 
• Overbearing implies a tendency to be oppressively or rudely domineering: an overbearing customer demanding to see the manager.